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Patented Sept. 21, 1926.

UNITED STATES PATENT OFFICE.

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80 Drawing.

This invention relates to an improved photographic reversal process andmore particularly to a step therein for reventmg reversal. The improvedstep W1 be described 5 as inco rated in the process covered by my Patent0. 1,480,703, granted July 3, 1923. The principal steps of that processwere successively, exposure, development, removal or bleaching of thesilver image, clearing, I controlled re-e re, redevelopment and a finalfixing. If a tendenc to re-reversal was found by test to take p ace atthe second development, there was introduced a step to overcome thistendency, this step comprising 1 an alkali bath prior to IQ-GXPOSUI'Qand redevelopment.

I have since discovered cases of re-reverse] that were not satisfactorilovercome by this treatment and I have furt ier discov- 0 end that theseoccurred when a fresh bleaching or reversing both, such as is describedin step 4 of the patent, was used for the first time; but that thetendenc disappeared after the bath had been use a short time. 25 Furtherresearch disclosed the fact that this tendenc is not found when there ispresent in the leachin or reversigfi bath a small amount of a ublesilver t. im roved step consists in the condil0 tionlng c this reversalor bleaching bath by the purposeful addition thereto of such a.solution. This conditicni ma; be accomplished in various ways, 0 whichthe folowing is an instance. To one liter of a bath I made in accordancewith the formula given in step 4 of said patent may be adde 2%; cc. ofa'10% solution of silver nitrate. A second method of introducing thesoluble Silver salt, useful when a continuous machine 40 such as isdescribed in my application Serial No. 618,846, filed February 3, 1928,is used is to run a strip of waste film through the machine includinthebleaching bath 1'10! o its use in regufiar work. This won (1 be Idone by fogging such a strip and using it as a leader for the regularfilm, then drawing it throu h the developing and bleaching baths. 'fiieaction of t e b caching bath on the developed silver of the waste striwould introduce silver salt into the bat The length of such a stripwould have to be ascertained by ex rilnent under the conditions presentin e actual apparatus. A third Application fled January s1, ms. and In.em.

way of attaining the desired object is to add to a newly pre ared bath aqgantity of ii aid from a or exhausted leaching bat and this quantity;wouldnleo, of course, have to be determined b experiment and the actualcondition content of the used hath. However, the first method mentionedgives a precise step available to those without experience.

Tlge re-revgreal rgenticnled ishusually a com ination o nega 've an 'veiand not a complete re-reversn f lt refit? appear most strongly whenthere was originally an under-ex are in the camera, Since in such casest ere is little silver in the developed image and thebleaching bath isslow to acquire a silver salt from its action on this thin image. Ifthee incl developed image is very ense, the ten encyjo re-reversedisappears much more uickly because of the re d formation 0 the silversalt in the blee ing bath. II

This invention is of particular use in the reversal procem described inm atent in which the re-exposure is contro e -and in which all thesensitive silver salts are not usually redevelc because re-reversalcannot occur in t e usual reversal processes wherein all the sensitivesilver salts are redevelo d.

e theory pnderlyin the cause and prevention of this type 0 re-reversalis obscure.

As stated in the patent, the preferred reversing bath is as ollows:

Potassium permanganate (4% so- As described in the patent, the bathcontains about 1% of sulphhuric acid, and the silver salt formed in ebleaching o eration is silver sulfate. When silver nitrate is added tothe bath it is transformed into silver sulfate. When silver salts lesssoluble than the sulfate, such as the halides, are added, the result isnot obtained. It ap rs to be necessary to use a salt which w: l betransformed into the salt of the acid of the bleaching bath, in thiscase the sulfate.

The bath as used substantially contains silver salt to produce asaturated solution of silver sulfate in the bath. The solubility of thesulfate increases with the acidity of the bath and as the acidity of thebath may vary, as was stated in the patent, the amount of sulfate maycorrespondingly vary.

In each of the various methods mentioned above it will be seen that thissalt is incorpo-' rated in the bath .when it is initially used for itsintended purpose.

Having thus described my invention what I claim is new and desire tosecure by Letters Patent is:

1. The method of conditioning an acid bath for use in a photographicreversal procase for bleachingra silver image preparatory toIve-development that comprises the incorration therein of a silver saltcorrespond-v mg to the acid of the bath.

2. The method of conditioning a bath containing sulfuric acid for use ina' hatephlc reversal process for bleaching a silver image preparatory tore-development that comprises t e incorporation therein of silversulfate.

3. The method of conditionin a bath comprising a permanganate ansulfuric acid for use as a bleaching bath for a silver image preparatoryto re-development thereof with a silver ima e to an acid bleaching bathand to a rediaveloping bath, the improved step that comprises using forbleachmg a bath that has initially present a silver as t of the acid ofthe bath. 5. In a photographic reversal process comprising successive ysubmitting a carrier with a silver image to a bleaching bath containingsulfuric acid and then to a redeveloping bath, the improved step thatcomprises using for bleaching a bath that has silver sulfate initiallypresent.

6. In a photographic reversal process comprising suocessive y submittinga carrier with a silver image to a bleachin bath containin apermanganate and an furic acid and t en to a redeveloping bath, theimproved step that comprises usin for bleachmg a bath that has silversul ate initially present.

Signed at Rochester, New York, this 29th day of January 1925.

I JOHN G. CAPSTAFF.

silver sulfate in the bath. The solubility of the sulfate increases withthe acidity of the bath and as the acidity of the bath may vary, as wasstated in the patent, the amount of sulfate may correspondingly vary.

In each of the various methods mentioned above it will be seen that thissalt is incorporated in the bath when it is initially used for itsintended purpose.

Having thus described my invention What I claim is new and desire tosecure by Let ters Patent is:

1. The method of conditioning an acid bath for use in a photographicreversal process for bleaching a silver image preparatory tore-development that comprises the incorporation therein of a silver saltcorresponding to the acid of the bath.

2. The method of conditioning a bath containing sulfuric acid for use ina photographic reversal process for bleaching a silver image preparatoryto re-development that comprises the incorporation therein of silversulfate.

3. The method of conditioning a bath comprising a permanganate andsulfuric acid for use as a bleaching bath for a silver image preparatoryto re-development thereof that comprises the incorporation therein ofsilver sulfate.

4. In a photographic reversal process comprising successively submittinga carrier with a silver image to an acid bleaching bath and to aredeveloping bath, the imroved step that comprises using for bleach mg abath that has initially present a silver salt of the acid of the bath.

5. In a photogra hic reversal process comprising successive y submittinga carrier with a silver image to a bleaching bath containing sulfuricacid and then to a redeveloping bath, the improved step that comprisesJOHN G. CAPSTAFF.

New York, this 29th Certificate of Correction. It is hereby certifiedthat in Letters Patent No. 1,600,797, granted September 21.

1.926, upon the application of John G.

(lapstaii, of Rochester, New York, for an improvement in ReversalProcesses. an error appears in the printed specification requiringcorrectimi as follows: Page therein that the same may con int ;n in

[swan] l. read rsermwmsul; and that the said h tters the record her, A.l). 1926.

lines 3 and 4, for the word reversal" Fatcnt should be read with thiscorrection oi? the case in the Patent Office.

\Vltl. A. h'liNNAN, Actny Lmrzmsaiii-mar of i afent-a.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1. 6fi0,797, grantedSeptember 21, 1926, upon the application of John G. (Tapsmfl, ofhochester, New York, for an improvement in Reversal Processes, an errorappears in the printed specification requiring COII'GC-UUD as foilnws:Page 1, lines 3 and 4, for the word reversal read res-reversal; and thatthe said Letters Patent should be remd with this correction therein thatthe same may conform to the record of the Case in the Patent Office.

Signed and sealed this 19th day of October, A. D. 1926.

[SEAL] WM. A. KINNAN,

Acting (iommissimer 0/ Pafents.

